1. Field of the Invention
This invention relates to the use of air pressure to perform the shifting functions in a power shift transmission, as well as combining the air shift valves with existing control levers for facilitating the operation of a front end loader.
2. Description of the Prior Art
In the standard modern day end loader, the common practice is to provide one pair of control levers for controlling the vertical and tilt operations of the bucket of the end loader, and one pair of control levers for forward reverse and range select controls for the power shift transmission of the end loader. The bucket controls are normally arranged for operation by one of the operator's hands while the transmission control levers are placed in proximity to the operator's opposite hand. Consequently, when need arises for controlling the forward or reverse motion of the machine while at the same time operating the bucket controls, the operator must remove both hands from the steering wheel of the machine, thus causing a potentially hazardous situation to arise. Furthermore, the ordinary transmission control consists of mechanical linkage elements which may become worn and loose, thereby causing a potential for missed shifts due to the linkage control lever not being moved to its limits by the operator. Accordingly, a need has arisen for a simple, safe and effective means of providing a compact control arrangement for end loaders which will obviate the above discussed deficiencies.
There are many known control arrangements for shifting transmissions and the like. Included among these is U.S. Pat. No. 2,445,716, issued Jul. 20, 1948, to Sternberg. The Sternberg device relates to truck transmissions utilizing a main transmission operated from a control lever and an auxiliary transmission operated from a rotary, finger operated lever mounted on the main control lever. U.S. Pat. No. 2,543,927, issued Mar. 6, 1951, to Montgomery, shows a gear shifting mechanism for a motorboat drive system. The Montgomery device includes a lever operating a cable which shifts a control valve which operate the slave cylinder to effect shifting of the transmission. U.S. Pat. No. 2,931,237, issued Apr. 5, 1960, to Backus, shows a gate-type remotely mounted shifting console and which has mounted thereon control valves for operating a pair of normally oriented slave cylinders for shifting a transmission. U.S. Pat. No. 3,863 518, issued Feb. 4, 1975, to Webber et al, shows an air operated transmission shifting system which includes neutraling means for automatically disengaging the vehicle drive line in the event of system malfunction.